Final answer:
The property used to differentiate between pure substances and mixtures is composition, with pure substances having a fixed composition and mixtures having varying compositions.
Step-by-step explanation:
The property used to differentiate between pure substances and mixtures is composition.
A pure substance is made up of only one type of particle and has a fixed composition, meaning it has a specific combination of elements or compounds. Examples of pure substances include elements like oxygen and compounds like water.
In contrast, a mixture is made up of multiple types of particles and can have varying compositions. It can be a combination of elements, compounds, or both. Examples of mixtures include saltwater (a mixture of salt and water) and air (a mixture of gases like nitrogen, oxygen, and carbon dioxide).
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